In recent years, power generation facilities which do no discharge greenhouse effect gases at the time of power generation and utilize recyclable energy are installed, and a reduction of carbon in a power supply system is examined. There has been examined supply of power based on interconnection of a dispersed power source such as a photovoltaic system, a wind turbine generator system, or a fuel cell system with an electric power system. When the dispersed power source is interconnected with the electric power system, a power conversion apparatus that converts power output from the dispersed power system in synchronization with the system is required.
This power conversion apparatus is configured to have the same capacity as that of the dispersed power source. When a place where the dispersed power source is installed is limited or a capacity of the single power conversion apparatus is not the same as a capacity of the dispersed power source, the power conversion apparatuses are connected in parallel to obtain a predetermined capacity. In parallel operations of the power conversion apparatuses, there is a method of transmitting a control timing or a direction value from a master device serving as a benchmark to a slave device using a communicating function and operating the master device and the slave device in synchronization with each other.